The present invention relates to a method for finishing resin-based dental restorations for human teeth and, in particular, to a method for contouring and polishing resin-based dental restorations.
The preparation of dental restorations for human teeth using resin-based materials, such as hybrid and microfill composites, compomers and similar materials, is well known in the art. The process of finishing such restorationsxe2x80x94i.e., contouring and polishing the restorations to create a natural appearancexe2x80x94can be a time-consuming multi-step process, requiring the use of several different tools. Typically, the resin-based restoration is first subject to initial contouring, using a diamond or tungsten carbide bur to roughly reproduce the occlusal anatomy of the tooth (as shown in FIG. 1a). The restoration is then fine contoured, using a tungsten carbide finishing bur to blend the restoration into the tooth and to characterize the restoration by creating developmental grooves, lobes, ridges and other secondary and tertiary anatomy (as shown in FIG. 1b). Once the restoration has been appropriately contoured, it is then smoothed using rubber finishing instruments, such as rubber discs, cups and points (as shown in FIG. 1c). Finally, the restoration is polished to create an enamel-like finish, using diamond or aluminum oxide polishing pastes applied by rubber cups and points (as shown in FIG. 1d).
Fine contouring and smoothing are the most important steps in the process of finishing a resin-based restoration. Creating a smooth and accurately defined transition or margin between the resin and the tooth extends the life of the restoration by reducing general wear and minimizing the risk of microleakage, chipping, staining and other wear problems that may cause deterioration of the restoration and increase the risk of recurrent caries.
In general, the step of fine contouring a resin-based restoration is performed using tungsten carbide burs in connection with high-speed, low-torque handpieces. The operation of the bur at high speeds is thought to permit rapid removal of material, thereby reducing the treatment time and minimizing the generation of frictional heat. However, the use of high-speed burs requires a high level of skill and attention. High-speed tungsten carbide burs rapidly and aggressively remove resin and enamel, thereby increasing the risk of accidental damage to the restoration and/or enamel of the tooth.
In addition, the operation of the bur at low torque limits the amount of pressure that can be applied to the bur. The inadvertent application of excessive pressure can cause the bur to unexpectedly seize up and stop rotating. As a result, the operator may lose control of the bur, allowing the bur to slip and gouge or chatter across the surface of the restoration and tooth, causing damage to the restoration and enamel of the tooth. Furthermore, high-speed burs must be operated under a constant spray of water to avoid generating frictional heat, which may cause damage to the restoration and tooth. This spray of water also creates a mist which can obscure the working area. These problems involved in using high-speed, low-torque burs are particularly acute in the case of posterior restorations, which are difficult to access and visualize, and which typically involve the reproduction of complex anatomy requiring firm control over the bur.
Consequently, the step of fine contouring the restoration using high-speed, low-torque burs must be performed by removing the material in small steps, using light contact pressure to minimize the risk of inadvertently damaging the restoration or enamel of the tooth. As a result, the process of finishing restorations can be time consuming and tedious, requiring a high degree of skill and patience.
In addition, these operating conditions make it difficult for the operator to adequately control the bur during the step of fine contouring the restoration. In particular, the use of firm and continuous pressure is often required to permit the precise control of the bur needed to create a smooth and accurately defined margin between the resin and the tooth. The inability to fine contour an accurately defined margin cannot be corrected in the subsequent smoothing and polishing steps. The rubber instruments used in smoothing and polishing do not contour the resin, but merely smooth the already contoured surface of the restoration. Moreover, excessive working of the restoration using rubber instruments can cause the rubber to deteriorate, resulting in the incorporation of rubber particles into the surface of the resin. Finally, it is essential to be able to create smooth and accurately defined margins in the fine contouring step.
Thus, there is need for a method of finishing resin-based dental restorations which reduces the risk of inadvertent damage to the restoration and enamel of the tooth, by providing greater control over the bur and improved visualization of the work area during the step of fine contouring. Furthermore, there is a need for a method of finishing resin-based restorations which is less time consuming, and which requires fewer instruments and finishing steps.
These needs and other needs are satisfied by the present invention, which comprises a method of preparing a dental restoration using a resin based material wherein the steps of fine contouring the restoration and creating a smooth transition between the resin-based material and tooth are performed in a single step, using a low speed, high torque bur.